[kernel/f21] CVE-2014-5077 sctp: fix NULL ptr dereference (rhbz 1122982 1123696)
Josh Boyer
jwboyer at fedoraproject.org
Mon Jul 28 13:49:07 UTC 2014
commit 1416cd4c0bb366c2fdf5ae5b027e2be973d7f5df
Author: Josh Boyer <jwboyer at fedoraproject.org>
Date: Mon Jul 28 09:46:02 2014 -0400
CVE-2014-5077 sctp: fix NULL ptr dereference (rhbz 1122982 1123696)
kernel.spec | 9 +
...p-inherit-auth_capable-on-INIT-collisions.patch | 212 ++++++++++++++++++++
2 files changed, 221 insertions(+), 0 deletions(-)
---
diff --git a/kernel.spec b/kernel.spec
index 3a3883e..86b1bd0 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -647,6 +647,9 @@ Patch25120: selinux-4da6daf4d3df5a977e4623963f141a627fd2efce.patch
# git clone ssh://git.fedorahosted.org/git/kernel-arm64.git, git diff master...devel
Patch30000: kernel-arm64.patch
+#CVE-2014-5077 rhbz 1122982 1123696
+Patch25124: net-v2-net-sctp-inherit-auth_capable-on-INIT-collisions.patch
+
# END OF PATCH DEFINITIONS
%endif
@@ -1380,6 +1383,9 @@ ApplyPatch kernel-arm64.patch -R
%endif
%endif
+#CVE-2014-5077 rhbz 1122982 1123696
+ApplyPatch net-v2-net-sctp-inherit-auth_capable-on-INIT-collisions.patch
+
# END OF PATCH APPLICATIONS
%endif
@@ -2255,6 +2261,9 @@ fi
# ||----w |
# || ||
%changelog
+* Mon Jul 28 2014 Josh Boyer <jwboyer at fedoraproject.org>
+- CVE-2014-5077 sctp: fix NULL ptr dereference (rhbz 1122982 1123696)
+
* Mon Jul 28 2014 Josh Boyer <jwboyer at fedoraproject.org> - 3.16.0-0.rc7.git0.1
- Linux v3.16-rc7
- Disable debugging options.
diff --git a/net-v2-net-sctp-inherit-auth_capable-on-INIT-collisions.patch b/net-v2-net-sctp-inherit-auth_capable-on-INIT-collisions.patch
new file mode 100644
index 0000000..73bad52
--- /dev/null
+++ b/net-v2-net-sctp-inherit-auth_capable-on-INIT-collisions.patch
@@ -0,0 +1,212 @@
+Bugzilla: 1123696
+Upstream-status: Queued for 3.16
+
+From patchwork Tue Jul 22 13:22:45 2014
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: [net,v2] net: sctp: inherit auth_capable on INIT collisions
+From: Daniel Borkmann <dborkman at redhat.com>
+X-Patchwork-Id: 372475
+Message-Id: <1406035365-1154-1-git-send-email-dborkman at redhat.com>
+To: davem at davemloft.net
+Cc: jgunthorpe at obsidianresearch.com, netdev at vger.kernel.org,
+ linux-sctp at vger.kernel.org, Vlad Yasevich <vyasevich at gmail.com>
+Date: Tue, 22 Jul 2014 15:22:45 +0200
+
+Jason reported an oops caused by SCTP on his ARM machine with
+SCTP authentication enabled:
+
+Internal error: Oops: 17 [#1] ARM
+CPU: 0 PID: 104 Comm: sctp-test Not tainted 3.13.0-68744-g3632f30c9b20-dirty #1
+task: c6eefa40 ti: c6f52000 task.ti: c6f52000
+PC is at sctp_auth_calculate_hmac+0xc4/0x10c
+LR is at sg_init_table+0x20/0x38
+pc : [<c024bb80>] lr : [<c00f32dc>] psr: 40000013
+sp : c6f538e8 ip : 00000000 fp : c6f53924
+r10: c6f50d80 r9 : 00000000 r8 : 00010000
+r7 : 00000000 r6 : c7be4000 r5 : 00000000 r4 : c6f56254
+r3 : c00c8170 r2 : 00000001 r1 : 00000008 r0 : c6f1e660
+Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
+Control: 0005397f Table: 06f28000 DAC: 00000015
+Process sctp-test (pid: 104, stack limit = 0xc6f521c0)
+Stack: (0xc6f538e8 to 0xc6f54000)
+[...]
+Backtrace:
+[<c024babc>] (sctp_auth_calculate_hmac+0x0/0x10c) from [<c0249af8>] (sctp_packet_transmit+0x33c/0x5c8)
+[<c02497bc>] (sctp_packet_transmit+0x0/0x5c8) from [<c023e96c>] (sctp_outq_flush+0x7fc/0x844)
+[<c023e170>] (sctp_outq_flush+0x0/0x844) from [<c023ef78>] (sctp_outq_uncork+0x24/0x28)
+[<c023ef54>] (sctp_outq_uncork+0x0/0x28) from [<c0234364>] (sctp_side_effects+0x1134/0x1220)
+[<c0233230>] (sctp_side_effects+0x0/0x1220) from [<c02330b0>] (sctp_do_sm+0xac/0xd4)
+[<c0233004>] (sctp_do_sm+0x0/0xd4) from [<c023675c>] (sctp_assoc_bh_rcv+0x118/0x160)
+[<c0236644>] (sctp_assoc_bh_rcv+0x0/0x160) from [<c023d5bc>] (sctp_inq_push+0x6c/0x74)
+[<c023d550>] (sctp_inq_push+0x0/0x74) from [<c024a6b0>] (sctp_rcv+0x7d8/0x888)
+
+While we already had various kind of bugs in that area
+ec0223ec48a9 ("net: sctp: fix sctp_sf_do_5_1D_ce to verify if
+we/peer is AUTH capable") and b14878ccb7fa ("net: sctp: cache
+auth_enable per endpoint"), this one is a bit of a different
+kind.
+
+Giving a bit more background on why SCTP authentication is
+needed can be found in RFC4895:
+
+ SCTP uses 32-bit verification tags to protect itself against
+ blind attackers. These values are not changed during the
+ lifetime of an SCTP association.
+
+ Looking at new SCTP extensions, there is the need to have a
+ method of proving that an SCTP chunk(s) was really sent by
+ the original peer that started the association and not by a
+ malicious attacker.
+
+To cause this bug, we're triggering an INIT collision between
+peers; normal SCTP handshake where both sides intent to
+authenticate packets contains RANDOM; CHUNKS; HMAC-ALGO
+parameters that are being negotiated among peers:
+
+ ---------- INIT[RANDOM; CHUNKS; HMAC-ALGO] ---------->
+ <------- INIT-ACK[RANDOM; CHUNKS; HMAC-ALGO] ---------
+ -------------------- COOKIE-ECHO -------------------->
+ <-------------------- COOKIE-ACK ---------------------
+
+RFC4895 says that each endpoint therefore knows its own random
+number and the peer's random number *after* the association
+has been established. The local and peer's random number along
+with the shared key are then part of the secret used for
+calculating the HMAC in the AUTH chunk.
+
+Now, in our scenario, we have 2 threads with 1 non-blocking
+SEQ_PACKET socket each, setting up common shared SCTP_AUTH_KEY
+and SCTP_AUTH_ACTIVE_KEY properly, and each of them calling
+sctp_bindx(3), listen(2) and connect(2) against each other,
+thus the handshake looks similar to this, e.g.:
+
+ ---------- INIT[RANDOM; CHUNKS; HMAC-ALGO] ---------->
+ <------- INIT-ACK[RANDOM; CHUNKS; HMAC-ALGO] ---------
+ <--------- INIT[RANDOM; CHUNKS; HMAC-ALGO] -----------
+ -------- INIT-ACK[RANDOM; CHUNKS; HMAC-ALGO] -------->
+ ...
+
+Since such collisions can also happen with verification tags,
+the RFC4895 for AUTH rather vaguely says under section 6.1:
+
+ In case of INIT collision, the rules governing the handling
+ of this Random Number follow the same pattern as those for
+ the Verification Tag, as explained in Section 5.2.4 of
+ RFC 2960 [5]. Therefore, each endpoint knows its own Random
+ Number and the peer's Random Number after the association
+ has been established.
+
+In RFC2960, section 5.2.4, we're eventually hitting Action B:
+
+ B) In this case, both sides may be attempting to start an
+ association at about the same time but the peer endpoint
+ started its INIT after responding to the local endpoint's
+ INIT. Thus it may have picked a new Verification Tag not
+ being aware of the previous Tag it had sent this endpoint.
+ The endpoint should stay in or enter the ESTABLISHED
+ state but it MUST update its peer's Verification Tag from
+ the State Cookie, stop any init or cookie timers that may
+ running and send a COOKIE ACK.
+
+In other words, the handling of the Random parameter is the
+same as behavior for the Verification Tag as described in
+Action B of section 5.2.4.
+
+Looking at the code, we exactly hit the sctp_sf_do_dupcook_b()
+case which triggers an SCTP_CMD_UPDATE_ASSOC command to the
+side effect interpreter, and in fact it properly copies over
+peer_{random, hmacs, chunks} parameters from the newly created
+association to update the existing one.
+
+Also, the old asoc_shared_key is being released and based on
+the new params, sctp_auth_asoc_init_active_key() updated.
+However, the issue observed in this case is that the previous
+asoc->peer.auth_capable was 0, and has *not* been updated, so
+that instead of creating a new secret, we're doing an early
+return from the function sctp_auth_asoc_init_active_key()
+leaving asoc->asoc_shared_key as NULL. However, we now have to
+authenticate chunks from the updated chunk list (e.g. COOKIE-ACK).
+
+That in fact causes the server side when responding with ...
+
+ <------------------ AUTH; COOKIE-ACK -----------------
+
+... to trigger a NULL pointer dereference, since in
+sctp_packet_transmit(), it discovers that an AUTH chunk is
+being queued for xmit, and thus it calls sctp_auth_calculate_hmac().
+
+Since the asoc->active_key_id is still inherited from the
+endpoint, and the same as encoded into the chunk, it uses
+asoc->asoc_shared_key, which is still NULL, as an asoc_key
+and dereferences it in ...
+
+ crypto_hash_setkey(desc.tfm, &asoc_key->data[0], asoc_key->len)
+
+... causing an oops. All this happens because sctp_make_cookie_ack()
+called with the *new* association has the peer.auth_capable=1
+and therefore marks the chunk with auth=1 after checking
+sctp_auth_send_cid(), but it is *actually* sent later on over
+the then *updated* association's transport that didn't initialize
+its shared key due to peer.auth_capable=0. Since control chunks
+in that case are not sent by the temporary association which
+are scheduled for deletion, they are issued for xmit via
+SCTP_CMD_REPLY in the interpreter with the context of the
+*updated* association. peer.auth_capable was 0 in the updated
+association (which went from COOKIE_WAIT into ESTABLISHED state),
+since all previous processing that performed sctp_process_init()
+was being done on temporary associations, that we eventually
+throw away each time.
+
+The correct fix is to update to the new peer.auth_capable
+value as well in the collision case via sctp_assoc_update(),
+so that in case the collision migrated from 0 -> 1,
+sctp_auth_asoc_init_active_key() can properly recalculate
+the secret. This therefore fixes the observed server panic.
+
+Fixes: 730fc3d05cd4 ("[SCTP]: Implete SCTP-AUTH parameter processing")
+Reported-by: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
+Signed-off-by: Daniel Borkmann <dborkman at redhat.com>
+Tested-by: Jason Gunthorpe <jgunthorpe at obsidianresearch.com>
+Cc: Vlad Yasevich <vyasevich at gmail.com>
+Acked-by: Vlad Yasevich <vyasevich at gmail.com>
+---
+ v1 -> v2, more notes:
+
+ I've only updated the commit description for now, this bug seems
+ clear to me that we would need to fix it; since RFC4895 mentions
+ it explicitly that on collisions, we need to *update* these params
+ accordingly as we would do so in RFC2960. So in other words, this
+ can be explained by having an *inconsistency* when doing the update
+ as auth_capable is *tightly coupled* with peer_random, peer_chunks,
+ peer_hmacs and eventually the asoc_shared_key creation.
+
+ For the rest, I went through the code and currently could not
+ find where we could oops if we don't have the others for now. It
+ needs more time and testing however. It's also not too clear from
+ RFC2960/RFC4960 what needs to be carried over in addition: so we
+ know "The endpoint should stay in or enter the ESTABLISHED state
+ but it MUST update its peer's Verification Tag from the State
+ Cookie, stop any init or cookie timers that may running and send
+ a COOKIE ACK." and we know that we need to update all AUTH related
+ members, which we do *now*.
+
+ In addition, we also need to fix AUTH + COOKIE_ECHO collisions,
+ as they currently cannot be resolved properly into a handshake.
+
+ net/sctp/associola.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/net/sctp/associola.c b/net/sctp/associola.c
+index 9de23a2..06a9ee6 100644
+--- a/net/sctp/associola.c
++++ b/net/sctp/associola.c
+@@ -1097,6 +1097,7 @@ void sctp_assoc_update(struct sctp_association *asoc,
+ asoc->c = new->c;
+ asoc->peer.rwnd = new->peer.rwnd;
+ asoc->peer.sack_needed = new->peer.sack_needed;
++ asoc->peer.auth_capable = new->peer.auth_capable;
+ asoc->peer.i = new->peer.i;
+ sctp_tsnmap_init(&asoc->peer.tsn_map, SCTP_TSN_MAP_INITIAL,
+ asoc->peer.i.initial_tsn, GFP_ATOMIC);
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